One of the core principles of scientific skepticism is that human perception, information processing, and memory, while powerful, are deeply flawed. We need rigorous controls in observation and analysis in order to compensate for these flaws and arrive at reliable conclusions. Otherwise we are slaves to the vagaries of our own neurological function.

One of the coolest and most dramatic examples of our flawed perception is the phenomenon known as inattentional blindness. Before I go any further, for any of you who have not seen the basketball demonstration, take a look at it now before you continue reading. See if you can count how many times the players in the white shirt pass the ball around. This is more tricky than it seems.

Cool, eh. Most people do not see the gorilla. I have shown this video several times at lectures, and only about 20-30% of people typically see the gorilla. Those who did not see it often insist that it was not there the first time – it is simply difficult to believe that they could have missed something so blatant. But they did. I missed it the first time I viewed the video.

The concept is actually quite simple – in order to focus our attention on one thing we filter out distracting information. We are therefore blind to the distracting information, blind due entirely to lack of attention to it, hence inattentional blindness. The more we focus on one thing, the greater this effect is.

A recent study by Ira Hyman et al asked whether or not the increased risk of accidents from talking on cell phones while driving is due to inattentional blindness. It has been well established that talking on a cell phone while driving is distracting and comes with an increased risk of accidents. This has led to hands-free laws in some states, but the evidence also suggests that this does not help. The problem does not derive from using a hand to hold the phone, but the diversion of attention to the conversation. Meanwhile, the same risk is not present from talking to a passenger in the car.

Hyman designed a pair of studies where he had subjects walk across a certain path without distraction, while listening to an iPod, while talking on a cell phone, and while walking and talking with another person. He found in the first study that people talking on a cell phone walked more slowly, and had to make more course corrections than the other groups.

In the second study he place a unicycling clown (yes – the one in the picture above) along the path, in a location that should have been clearly visible. He found:

Only 25% of the cell phone users had noticed the clown and many turned around at that point to see what they had missed. In essence, 75% of the cell phone users experienced inattentional blindness to the unicycling clown. In contrast, over half of the people in the other conditions reported seeing the clown (51% of single individuals, 61% of music player users, and 71% of people in pairs).

So talking on a cell phone cut in half the probability of seeing the clown. Listening on a music player had a slightly increased chance of seeing the clown. Either this is statistical noise, and there was no real effect, or alternatively listening to music may make us slightly more attentive. (Sounds like a question for further research.) Walking with a buddy resulted in almost exactly what we would predict from adding the individual chances of seeing the clown independently.

What this all might mean is that there is something about talking on a cell phone that is particularly demanding of our attention – more so than listening to music or talking with someone who is physically present. These results also support the hypothesis that talking with a passenger is not as dangerous because the extra pair of eyes increases the chance that someone will notice a sudden obstacle or unexpected traffic pattern.

To be clear, while this study supports prior research showing that talking on a cell phone while driving is dangerous, the study was not designed to measure the danger of talking on a cell phone, but rather why is talking on a cell phone dangerous. Their answer is that it is probably due, at least in part, to inattentional blindness.

But I do think this study reinforces the other lines of evidence showing that this behavior is risky. I would also like to see that same kind of research but looking at texting, which I suspect will be far worse than talking on a cell phone. But texting might involve more of diverting your gaze to the keyboard rather than consuming attention, but it may also involve both.

And the take home message should be crystal clear – don’t text, talk on cell phones, or engage in otherwise demanding or diverting activities while driving. But listening to music is OK, maybe even slightly helpful.

These studies and studies like them also demonstrate for me a broad principle – the more we understand how our own brains work, given that they are the most important tool we have, the better we will be able to use them.

27 Responses to “Have You Seen This Clown”

I really don’t get the basketball video. Maybe I’ve become too skeptical, and just always assume someone is trying to screw with me. Steve, you must be joking. There has to be something else in that video that I am missing and the “most people miss the gorilla” thing is just a distraction from what is really going on… right? You’re saying that people are so distracted by people tossing basketballs around that they don’t see a guy in a cheap gorilla suit walking right through the middle of the picture? I can’t even read your entire article because now I’m totally distracted by that idea. Thanks for screwing up my whole day, Steve. I’ll never be able to focus on work now.

Yes – most people do not see the gorilla walk right through the middle of the people tossing around the basket ball. That is it.

I do think prep matters, though. Given the intro from this blog entry, more people might be looking for something rather than really focusing on counting the tosses. When I use it in a lecture, I preface the video by saying that it is a test of observation, and that guys tend to be a bit better at counting the tosses than girls. This makes it competitive, and people really try hard, which enhances the inattentional blindness.

Yes. Prep was really important in my case. I saw this first at a Michael Shermer lecture. He brought it up in the context of a “Wisdom of the crowds” argument. He asked the audience to silently count how many times the students in black shirts pass the basketball, kind of like watching a shell game. He said he would take the median count and compare it to the true number of passes. It was all a ruse, of course.

This setup further distracted the audience and I almost missed the gorilla (I caught him right as he was leaving the screen).

I am curious if listening to a podcast or an audio book gives similar results as talking on a cellphone (can I safely listen to SGU while driving for instance ;-)). And I’m also curious to know how they instructed the talking couple. I think that it is crucial that the conversation they have required a similar amount of concentration and focus as the cellphone conversation otherwise the comparison is very weak.

I wonder if using a phone while driving is something that can be learnt. My grandfather believed it was impossible for anyone to drive over 30mph safely, and perhaps it was when he learnt to drive. It would be interesting to see a study comparing the amount of time that the participants have used cellphones. Would people who have used them for 10-15 years be less likely to experience inattention? How about older people who’ve only used a phone for a few years? How about young people who’ve used one since they were 10 years old?

Has any study been done to try and find out why people don’t mind being distracted while driving? Do people even know that they are being distracted? Do they understand the concept of ‘distraction’? (I regularly see drivers blow through stopsigns at full speed. Things are getting dangerous.)

Yes, when asked to count the number of passes, and when you are not suspecting deception, the gorilla becomes almost invisible. Me and most people I know didn’t see the gorilla, especially when presented in the right way.

This also reminds me of last weekend, eating dinner with my family. I was giving my take in a discussion on an abstract subject, while my sister sitting next to me handed me a plate so, another family member could pour some food on it. I took the plate, but didn’t even realize I was holding it, until my sister grew impatient. All my focus was on the conversation.

When you talk to someone, you haven’t always figured out exactly what you are going to say before you start talking, though you have a general idéa of what to say. Something as mundane as constructing sentences takes focus. I.e. if you are trying to explain something complex to someone, it is pretty impossible to follow another conversation in the vicinity simultaneously, without a great loss in information in one of the conversations.

The setup for the Gorilla video when I first saw it was “count the passes of the people in white shirts”.

As for inattentional blindness with cell phones, etc, it’s going to be a bit like putting the genie back in the bottle at this point. I just don’t think we will be very successful trying to change people’s behavior in this area.

I missed the Gorilla the first time I saw the video, as did about 80% of my 50-person class. It was shown in a lecture for one of my Public health courses, with the appropriate setup of counting passes and basketballs etc. I was flabbergasted when the video finished, the professor turned on the lights, and said “how many of you saw the gorilla?” I thought it was some weird joke until about 10 people put their hands up, and the rest of the class looked at the prof with bewilderment until he replayed the video.

The first time I saw the basketball demonstration it was by way of a link to a youtube video from this very blog. The setup is included in the video and there are a few more players on either team. http://www.youtube.com/watch?v=UfA3ivLK_tE

It’s hard to compare which is the better version once you know what it’s all about. Perhaps someone here can show both versions to someone not familiar with them and see if there is any difference (I think I showed the other version to just about everyone I would be comfortable showing it to). I would suspect that the bear is less likely to be spotted, but the gorilla has a bigger impact if missed.

dwayne, was that supposed to be funny? Are we supposed to believe you didn’t replay the clip and therefor wouldn’t know better than to pretend you saw a black player? Or do your ninjas come in blackface?

I’d be willing to bet that navigating an IPod is about as bad as texting.

I also wonder if there is a difference in listening to music versus an audio book. I like to listen to books when I’m driving because it keeps me awake and alert. My wife on the other hand gets too involved in the book and doesn’t pay attention to traffic, so she won’t listen to them.

Shamar – what this paper shows is that there is inattentional blindness while talking on a cell phone and walking. The point was to see if talking on a cell phone produces inattentional blindness, and this hypothesis seems to be confirmed by this study. It is perfectly internally consistent.

What you mean is you doubt if these findings can be extrapolated to explain the independently documented increased risk of talking on a cell phone while driving. That will require more study to confirm, but at least this study showed that inattentional blindness is a plausible explanation.

The fact that driving requires more attention than walking does not necessarily discount inattentional blindness – in fact all it really means is the effects of inattentional blindness are likely to be more severe while driving.

The obvious follow up study is to do a similar protocol with driving. This will have to be done on a closed course, however, under very controlled conditions.

I, too, did not see the gorilla the first time. I was told to count the passes of the players in white. I wonder if counting the players wearing black would increase the odds of spotting the gorilla since you would be watch the colour more?

Juga, I would be surprised if it can be learned. Talking to people hasn’t changed much in many years. However, car design and handling and well has road conditions have improved drastically over your grandfathers lifetime.

Also, I’m sure the SGU covered a recent study on multi-tasking that showed those who think they are good at it are not and had something to do with the process of attention switching between two different types of tasks. Talking and walking (in this study) are pretty different types of tasks. Drive should require even more attention to even more sensory input at a faster rate, which probably provides more opportunity for distraction.

Like all good studies, this just raises even more questions and further study ideas to tease out the workings of the brain.

One thing is for sure, the way our brains work never ceases to surprise me and fascinate me. It is nice to have some good guides to explain it all to me and Steve is among the best.

I wonder how much of the inattentional blindness with cell phones has to do with having only auditory input, and w/cell phones often garbled auditory input at that. Is it necessary to keep more of what we hear in our working memory in order to comprehend it?

I’m curious what would happen w/the dyad walking together if they could somehow be wired up to only hear one another through headphones and not have any visual cues. Would it increase the risk of inattentional blindness close to that of talking on a cell phone?

I was already well aware of this type of study, so I’m not surprised I noticed the gorilla. Also I am suspicious of these things so I watch them by trying to un-focus my eyes and use my “peripheral” vision rather than focus on what is happening (as a side note it’s surprising how little difference it makes watching these things in this way.. at least in small apparent angle videos).
However.. I have to say I didn’t consciously notice the gorilla till it was almost in the middle of the video. The fact the non-white shirts are black… almost identical to the black shirts when the gorilla is side on. So it’s easy to see how it can be missed.

I assume it has to do with the limiting of our eyes natural vibrations and scanning patterns because we have expectations that something will happen where we are currently focused?
People never seem to believe this happens when you use this example though. I think a more common day experience is; for instance; when you try to point out a bird or something else in a tree. Until you “see” it… you can’t see anything. Once you focus on it… you have no idea how you could not see it.
The illusion of video camera style vision is so compelling its hard for me to walk down the road and truly accept I’m not “seeing” most of the scene my brain is painting for me.
Another reason reality is cooler than pseudoscience 🙂